Hydrocarbon conversion process

Abstract

This invention provides an integrated process for converting a hydrocarbon feedstock having components boiling above 300° F. into liquid fuel products boiling in the range of from about 80° F. to about 700° F., which process comprises passing said feedstock to a first stage hydrocracking zone to effect decomposition of organic sulfur and/or nitrogen compounds, passing a portion of the product from said first stage hydrocracking zone to a second stage hydrocracking zone, simultaneously passing the remaining portion of said product from said first stage hydrocracking zone to an aromatics saturation zone, and subsequently passing the product from said hydrocracking zone and said aromatics saturation zone to one or more fractionating zones wherein said products are separated into a tops fraction and a bottoms fraction, with the tops fraction being separated into light gasoline, naphtha, jet fuel and diesel fuel products, and a portion or all of the bottoms fraction being recycled to the hydrocracking zone and/or the aromatics saturation zone following the optional removal of heavies and polynuclear aromatics.

What is claimed is: 
     
       1. An integrated process for converting a hydrocarbon feedstock having components boiling above 300° F. into liquid fuel products boiling in the range of from about 80° F. to about 700° F., which process comprises: a) passing said hydrocarbon feedstock in the presence of a hydrogen source and at least one first stage hydrocracking catalyst through a first stage hydrocracking zone at an elevated temperature and pressure to effect decomposition of organic sulfur and/or nitrogen compounds contained therein with limited cracking of hydrocarbons,   b) passing a portion of the product from said first stage hydrocracking zone to a second stage hydrocracking zone wherein said portion of the product is contacted at elevated pressure and a temperature in the range of from about 400° F. to about 1000° F. with a hydrogen source and at least one second stage hydrocracking catalyst comprising one or more hydrogenating components selected from the group consisting of Group VIB metals, oxides, sulfides, Group VIII metals, oxides, sulfides and mixtures thereof supported on a carrier having hydrocracking activity,   c) passing the remaining portion of said product from said first stage hydrocracking zone to an aromatics saturation zone wherein said remaining portion of the product is contacted at elevated pressure and a temperature in the range of from about 300° F. to about 700° F. with a hydrogen source and an aromatics saturation catalyst comprising one or more Group VIII noble metal hydrogenation components on a support selected from an amorphous support and a zeolitic support,   d) passing the products from said second stage hydrocracking zone and said aromatics saturation zone to one or more fractionating zones wherein said products are separated into a tops fraction and a bottoms fraction, and   e) recovering liquid fuel products boiling in the range of from about 80° F. to about 700° F. from the tops fraction.   
     
     
       2. The process of claim 1 wherein said first stage hydrocracking catalyst comprises a component selected from the group consisting of Group VIB metals, oxides, sulfides, Group VIII metals, oxides, sulfides and mixtures thereof, supported on an amorphous carrier. 
     
     
       3. The process of claim 1 wherein said first stage hydrocracking is carried out in such a way that the sulfur level of the hydrocarbon feedstock is reduced to below about 500 parts per million and the nitrogen level of the hydrocarbon feedstock is reduced to below about 50 parts per million. 
     
     
       4. The process of claim 3 wherein said first stage hydrocracking zone is operated at a temperature ranging from about 600° F. to about 800° F. and a pressure ranging from about 500 psig to about 5,000 psig. 
     
     
       5. The process of claim 1, wherein an amount of product from said first stage hydrocracking zone in the range of from about 5 percent by volume to about 95 percent by volume, basis the total volume of the product from the first stage hydrocracking zone, is sent to the second stage hydrocracking zone. 
     
     
       6. The process of claim 5, wherein an amount of product from said first stage hydrocracking zone in the range of from about 25 percent by volume to about 75 percent by volume, basis the total volume of the product from the first stage hydrocracking zone, is sent to the second stage hydrocracking zone. 
     
     
       7. The process of claim 1 wherein said second stage hydrocracking catalyst comprises a Group VIB component selected from the group consisting of tungsten, molybdenum and mixtures thereof, a Group VIII component selected from the group consisting of nickel, cobalt and mixtures thereof, and a carrier selected from molecular sieves having a pore diameter greater than about six angstroms admixed with an inorganic oxide binder selected from the group consisting of alumina, silica, silica-alumina and mixtures thereof. 
     
     
       8. The process of claim 7 wherein the Group VIII component is nickel, the Group VIB component is selected from the group consisting of molybdenum, tungsten and mixtures thereof, the molecular sieve is zeolite Y and the binder is alumina. 
     
     
       9. The process of claim 1 wherein said second stage hydrocracking zone is operated at a temperature ranging from about 500° F. to about 900° F. and a pressure ranging from about 500 psig to about 5,000 psig. 
     
     
       10. The process of claim 1, wherein an amount of product from said first stage hydrocracking zone in the range of from about 5 percent by volume to about 95 percent by volume, basis the total volume of the product from the first stage hydrocracking zone, is sent to the aromatics saturation zone. 
     
     
       11. The process of claim 10, wherein an amount of product from said first stage hydrocracking zone in the range of from about 25 percent by volume to about 75 percent by volume, basis the total volume of the product from the first stage hydrocracking zone, is sent to the aromatics saturation zone. 
     
     
       12. The process of claim 1 wherein said catalyst in the aromatics saturation zone comprises one or more Group VIII noble metal(s) supported on a zeolitic support comprising a modified Y zeolite having a unit cell size between 24.18 and 24.35 Å and a SiO 2  /Al 2  O 3  molar ratio of at least 25. 
     
     
       13. The process of claim 1 wherein said catalyst in the aromatics saturation zone comprises one or more Group VIII noble metal(s) supported on a zeolitic support comprising a modified Y zeolite having a unit cell size between 24.20 and 24.30 Å and a SiO 2  /Al 2  O 3  molar ratio of at least 25. 
     
     
       14. The process of claim 12 wherein said Group VIII noble metal is selected from the group consisting of palladium and mixtures of platinum and palladium. 
     
     
       15. The process of claim 1 wherein said aromatics saturation zone is operated at a temperature ranging from about 400° F. to about 675° F. and a pressure ranging from about 500 psig to about 5,000 psig. 
     
     
       16. The process of claim 1 wherein said bottoms fraction is recycled to the second stage hydrocracking zone. 
     
     
       17. The process of claim 1 wherein said bottoms fraction is recycled to the second stage hydrocracking zone and the aromatics saturation zone. 
     
     
       18. An integrated process for converting a hydrocarbon feedstock having components boiling above 300° F. into liquid fuel products boiling in the range of from about 80° F. to about 700° F., which process comprises: a) passing said hydrocarbon feedstock in the presence of a hydrogen source and at least one first stage hydrocracking catalyst through a first stage hydrocracking zone at an elevated temperature and pressure to effect decomposition of organic sulfur and/or nitrogen compounds contained therein with limited cracking of hydrocarbons,   b) passing from about 50 percent by volume to about 95 percent by volume, basis the total volume of the product from said first stage hydrocracking zone to a second stage hydrocracking zone wherein said portion of the product is contacted at elevated pressure and a temperature in the range of from about 400° F. to about 1000° F. with a hydrogen source and at least one second stage hydrocracking catalyst comprising a Group VIB component selected from the group consisting of tungsten, molybdenum and mixtures thereof, and a Group VIII component selected from the group consisting of nickel, cobalt and mixtures thereof, supported on a carrier selected from molecular sieves having a pore diameter greater than about six angstroms admixed with an inorganic oxide binder selected from the group consisting of alumina, silica, silica-alumina and mixtures thereof,   c) passing the remaining portion of said product from said first stage hydrocracking zone to an aromatics saturation zone wherein said remaining portion of the product is contacted at elevated pressure and a temperature in the range of from about 300° F. to about 675° F. with a hydrogen source and at least one aromatics saturation catalyst comprising one or more Group VIII noble metal(s) supported on a zeolitic support comprising a modified Y zeolite having a unit cell size between 24.20 and 24.30 Å and a SiO 2  /Al 2  O 3  molar ratio of at least 25,   d) passing the products from said second stage hydrocracking zone and said aromatics saturation zone to one or more fractionating zones wherein said products are separated into a tops fraction and a bottoms fraction,   e) recovering liquid fuel products boiling in the range of from about 80° F. to about 700° F. from the tops fraction, and   f) recycling the bottoms fraction.   
     
     
       19. The process of claim 18, wherein the amount of product from said first stage hydrocracking zone sent to the second stage hydrocracking zone is in the range of from about 75 percent by volume to about 90 percent by volume, basis the total volume of the product from the first stage hydrocracking zone. 
     
     
       20. An integrated process for converting a hydrocarbon feedstock having components boiling above 300° F. into liquid fuel products boiling in the range of from about 80° F. to about 700° F., which process comprises: a) passing said hydrocarbon feedstock in the presence of a hydrogen source and at least one first stage hydrocracking catalyst through a first stage hydrocracking zone at an elevated temperature and pressure to effect decomposition of organic sulfur and/or nitrogen compounds contained therein with limited cracking of hydrocarbons,   b) passing from about 50 percent by volume to about 95 percent by volume, basis the total volume of the product from said first stage hydrocracking zone to an aromatics saturation zone wherein said remaining portion of the product is contacted at elevated pressure and a temperature in the range of from about 300° F. to about 675° F. with a hydrogen source and at least one aromatics saturation catalyst comprising one or more Group VIII noble metal(s) supported on a support comprising a modified Y zeolite having a unit cell size between 24.20 and 24.30 Å and a SiO 2  /Al 2  O 3  molar ratio of at least about 25,   c) passing the remaining portion of said product from said first stage hydrocracking zone to a second stage hydrocracking zone wherein said portion of the product is contacted at elevated pressure and a temperature in the range of from about 400° F. to about 1000° F. with a hydrogen source and at lease one second stage hydrocracking catalyst comprising a Group VIB component selected from the group consisting of tungsten, molybdenum and mixtures thereof, and a Group VIII component selected from the group consisting of nickel, cobalt and mixtures thereof, supported on a carrier selected from molecular sieves having a pore diameter greater than about six angstroms admixed with an inorganic oxide binder selected from the group consisting of alumina, silica, silica-alumina and mixtures thereof,   d) passing the products from said second stage hydrocracking zone and said aromatics saturation zone to one or more fractionating zones wherein said products are separated into a tops fraction and a bottoms fraction,   e) recovering liquid fuel products boiling in the range of from about 80° F. to about 700° F. from the tops fraction, and   f) recycling the bottoms fraction.   
     
     
       21. The process of claim 20, wherein the amount of product from said first stage hydrocracking zone sent to the aromatics saturation zone is in the range of from about 70 percent by volume to about 90 percent by volume, basis the total volume of the product from the first stage hydrocracking zone.